1. Field of the Invention
The present invention relates to an electric coupling device for the terminal of an electric equipment unit.
This invention further relates to a circuitbreaker equipped with said device.
This invention is also concerned with an assembly of components for the manufacture of electric equipment units.
2. Description of the Prior Art
Certain types of electrical apparatus, in particular those equipped with overload relays such as circuit-breakers, pass currents having a value which is equal at most to that of the maximum adjustment current of the relay.
In order to adjust the maximum adjustment current of the relay as closely as possible to the current presumed to be absorbed by the receiver, manufacturers offer, for an equipment unit having a given rating, a range of current-overload relays in which the maximum adjustment values extend from a very low current value to the rated value of the apparatus. For obvious economic reasons, the electrical fitter will choose the section of coupling conductors as a function of the rating of the relay employed. The equipment unit or apparatus must consequently be provided with connection means which are suited for all cross-sections of conductors corresponding to current intensities within the range for which the apparatus is designed.
In practice, the connection means which ensure high quality of clamping of large-section conductors are liable to damage small-section conductors. It is therefore necessary to adapt the size or the type of connection means as a function of the cross-section of the conductor and consequently of the rating of the overcurrent relay employed.
It is possible for example to employ a connection device of the yoke type for one range of cross-sections of coupling conductors and a connection device of the cage type for another range.
In the yoke-type connection device, the wire is gripped between a movable gripping member or so-called yoke loosely mounted beneath the head of a screw which passes through the yoke, and a fixed gripping member having an internally-threaded bore in which the screw can be engaged so as to clamp the conductor between the two gripping members on either of the two sides of the screw. The stationary gripping member is usually a conductive strip connected to the electrical means contained within the equipment unit.
In the cage-type connection device, a screw can be engaged in an internally-threaded bore of the top of an annular cage of rectangular shape and carries at its free end located within the cage a loosely mounted gripping member having the function of clamping the conductor against a stationary gripping member which is applied against the inner face of the base of the cage.
The cage device is unsuitable for small-section conductors because these latter would be positioned in an uncertain manner between the stationary and movable gripping members and also because the developed clamping force would subject them to excessive stress. On the other hand, the yoke devices are unsuitable for large-section conductors since the available space on each side of the screw is unsufficient to introduce them.
Thus, although it may be postulated that two identical casings may contain electrical means such as an overcurrent relay which are adapted to very different current values such as 1 A and 80 A, for example, this possibility has been abandoned up to the present time since it has been found necessary to provide different casings as a function of the intended coupling so as to make them capable of housing connection devices of the cage or yoke type respectively. The cage devices are more cumbersome than the yoke devices. If it were desired to mount a yoke device within a housing provided within the casing for receiving a cage device, the movable gripping member would not be prevented from rotating by the walls of the housing and the wire to be gripped might be introduced at too great a lateral distance from the screw out of reach of the yoke, thus resulting in a faulty connection.
In point of fact, the need to provide two different casings for the two ranges of cross-sections of conductors produces a significant increase in the cost price of electrical apparatus.